1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device and in particular to a backlight control device and method of a liquid crystal display device.
2. Background of the Related Art
Generally, various handheld electronics equipped with an LCD, such as a notebook computer, a personal digital assistance (PDA) and a web pad, contain a backlight control device to control variable brightness or to maintain the brightness of the LCDs. FIG. 1 is a schematic block diagram showing a backlight control device of a related art LCD. As shown in FIG. 1, the backlight control device includes a backlight lamp 3 mounted on the back of an LCD 1 to emit light, and a translucent mirror 2 having an intermittent form with multiple slits evenly spread out is mounted in between the backlight lamp 3 and the LCD 1 to enable use of light sources from both the backlight lamp 3 and external or ambient light. A light-sensor 4 measures intensity of the external or surrounding light, and an A/D converter 5 converts an electric signal, detected and generated by the light-sensor 4, into a digital signal. A power supply 7 converts the battery power or the external power source into a fixed amount driving current and then supplies the driving current to the backlight lamp 3. A microcomputer 6 selectively stops the driving current to the backlight lamp 3 according to the intensity of surrounding light detected by the light-sensor 4 and the A/D converter 5. A keyboard 9 is for a user to provide input via keys, and a keyboard controller 8 is for outputting key values, in correspondence with the key inputs, through the microcomputer 6.
An LCD type, which can utilize light sources from the backlight lamp 3 and the external light by placing the translucent mirror 2 in between the LCD 1 and the backlight lamp 3, is normally referred to as a reflective liquid crystal display. The power supply 7 uses an inverter to convert power into the driving current having the fixed amount.
The power supply 7 converts and supplies power into the fixed amount driving current, for example, a minimum of 1 mA to a maximum of 6 mA current, according to control of the microcomputer 6. The driving current then either emits the backlight lamp 3, or the driving current of the backlight lamp 3 is selectively cut-off according to control of the microcomputer 6.
In the case where intensity of surrounding light, detected by the light-sensor 4, meets the necessary light intensity to maintain the brightness of the reflective LCD without the backlight, the microcomputer 6 operates and controls the power supply 7, as described above, to cut-off the power supplied into the backlight lamp 3. Therefore, when the external light is enough to maintain the brightness of the reflective LCD, unnecessary use of battery power, that is used to emit the backlight, is prevented.
However, as described above the related art LCD backlight control method has various disadvantages. There exists a demand to increase or maximize the limited battery life by controlling the backlight operation, which consumes approximately 30% more power, more efficiently in the handheld electronics equipped with a reflective LCD.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.
An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
Another object of the present invention is to provide a backlight control device and method for a liquid crystal display (LCD) that controls the brightness of a backlight of the LCD, which can utilize light sources from both the external light and the backlight, according to intensity of surrounding light.
Another object of the present invention is to provide a backlight control device and method for an LCD to control the backlight operation depending on an intensity of surrounding light within a selected backlight control range that is selected from a plurality of backlight control ranges.
Another object of the present invention is to provide a backlight control device and method for an LCD that controls backlight operations depending on an intensity of surrounding light within a selected backlight control range that is selected from backlight control ranges that are determined into various levels according to the intensity of surrounding light and use of a battery or an external power source.
In order to achieve at least the above objects in a whole or in part, a backlight control device of an LCD in accordance with the present invention includes a backlight device that is capable of providing light to a display, a single light-sensor, wherein the single light sensor detects intensity of the ambient light, a power supply that selects either a battery or an external power source as a power source to provide driving power of the backlight device, a power source detector that detects the power source that provides the driving power of the backlight device and a backlight control device that comprises a control unit that controls the power supply to apply a backlight driving current in proportion to the detected intensity of the ambient light within a selected one of a plurality of backlight control ranges, wherein the plurality of backlight control ranges are designated into levels according to the ambient light intensity and the power source.
To further achieve at least the above objects in a whole or in part, in accordance with the present invention there is provided a brightness control method of an LCD that includes detecting a selected one of a plurality of power sources supplying a backlight, detecting intensity of surrounding light impinging the LCD, determining a plurality of backlight control ranges having different levels according to the surrounding light intensity and a power source, selecting a range from the backlight control ranges according to the detected surrounding light intensity and the detected power source and controlling a backlight driving current in proportion to the detected surrounding light intensity according to the selected backlight control range applied to the backlight.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.